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</head>
<body class="bg-gray-50">
    <!-- Hero Section -->
    <section class="hero-gradient text-white py-20 px-4 md:px-0">
        <div class="container mx-auto max-w-5xl text-center">
            <h1 class="text-4xl md:text-5xl font-bold mb-6">Java HashMap 的演进与优化</h1>
            <p class="text-xl md:text-2xl opacity-90 mb-8">从 Java 1.7 到 Java 1.8 的性能飞跃</p>
            <div class="flex justify-center space-x-4">
                <div class="px-4 py-2 bg-white text-indigo-600 rounded-full font-semibold">哈希冲突处理</div>
                <div class="px-4 py-2 bg-white text-indigo-600 rounded-full font-semibold">扩容机制优化</div>
                <div class="px-4 py-2 bg-white text-indigo-600 rounded-full font-semibold">并发性能提升</div>
            </div>
        </div>
    </section>

    <!-- Main Content -->
    <main class="container mx-auto max-w-5xl py-12 px-4 md:px-0">
        <!-- Intro Section -->
        <section class="mb-16">
            <div class="bg-white rounded-xl shadow-md overflow-hidden p-8 card-hover">
                <div class="flex items-start">
                    <div class="feature-icon rounded-full flex items-center justify-center mr-6">
                        <i class="fas fa-bolt text-indigo-500 text-xl"></i>
                    </div>
                    <div>
                        <h2 class="text-2xl font-bold mb-4">Java HashMap 性能演进</h2>
                        <p class="text-gray-700 mb-4">在 Java 1.8 中，<code class="bg-gray-100 px-2 py-1 rounded">HashMap</code> 通过引入红黑树来处理长链表，优化了哈希计算方法和扩容机制，提供了更高效的性能。这些改进使得 <code class="bg-gray-100 px-2 py-1 rounded">HashMap</code> 在高冲突和大数据量的情况下表现得更加高效。</p>
                        <p class="text-gray-700">同时，Java 1.8 中 <code class="bg-gray-100 px-2 py-1 rounded">ConcurrentHashMap</code> 的改进也使得并发性能得到了显著提升。</p>
                    </div>
                </div>
            </div>
        </section>

        <!-- Comparison Section -->
        <section class="mb-16">
            <h2 class="text-3xl font-bold mb-8 text-center">Java 1.7 vs Java 1.8 核心差异</h2>
            
            <div class="grid md:grid-cols-2 gap-8">
                <!-- 冲突解决机制 -->
                <div class="bg-white rounded-lg shadow-md overflow-hidden">
                    <div class="p-6">
                        <h3 class="text-xl font-bold mb-4 flex items-center">
                            <i class="fas fa-project-diagram text-indigo-500 mr-3"></i>
                            冲突解决机制
                        </h3>
                        
                        <div class="space-y-4">
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-17 mr-2">Java 1.7</span>
                                    <span class="font-medium">链表结构</span>
                                </div>
                                <p class="text-gray-600 text-sm">使用链表解决哈希冲突，当多个键的哈希值相同时，冲突的键值对会被存储在链表中。</p>
                            </div>
                            
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-18 mr-2">Java 1.8</span>
                                    <span class="font-medium">链表+红黑树</span>
                                </div>
                                <p class="text-gray-600 text-sm">当链表长度超过阈值(默认为8)时，转换为红黑树，提供O(log n)的查找性能，显著优化高冲突场景。</p>
                            </div>
                        </div>
                    </div>
                </div>
                
                <!-- 扩容机制 -->
                <div class="bg-white rounded-lg shadow-md overflow-hidden">
                    <div class="p-6">
                        <h3 class="text-xl font-bold mb-4 flex items-center">
                            <i class="fas fa-expand-alt text-indigo-500 mr-3"></i>
                            扩容机制
                        </h3>
                        
                        <div class="space-y-4">
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-17 mr-2">Java 1.7</span>
                                    <span class="font-medium">简单扩容</span>
                                </div>
                                <p class="text-gray-600 text-sm">扩容时容量翻倍，所有键值对重新哈希迁移到新数组，O(n)操作，性能开销大。</p>
                            </div>
                            
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-18 mr-2">Java 1.8</span>
                                    <span class="font-medium">优化扩容</span>
                                </div>
                                <p class="text-gray-600 text-sm">保持类似机制但优化了哈希算法和重排逻辑，减少扩容性能开销。</p>
                            </div>
                        </div>
                    </div>
                </div>
                
                <!-- 性能优化 -->
                <div class="bg-white rounded-lg shadow-md overflow-hidden">
                    <div class="p-6">
                        <h3 class="text-xl font-bold mb-4 flex items-center">
                            <i class="fas fa-tachometer-alt text-indigo-500 mr-3"></i>
                            性能优化
                        </h3>
                        
                        <div class="space-y-4">
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-17 mr-2">Java 1.7</span>
                                    <span class="font-medium">基础实现</span>
                                </div>
                                <p class="text-gray-600 text-sm">没有特别的性能优化措施，提供基本的哈希表功能。</p>
                            </div>
                            
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-18 mr-2">Java 1.8</span>
                                    <span class="font-medium">多项优化</span>
                                </div>
                                <p class="text-gray-600 text-sm">优化哈希计算方法，使用更复杂的扰动算法减少冲突，提升整体性能。</p>
                            </div>
                        </div>
                    </div>
                </div>
                
                <!-- 并发处理 -->
                <div class="bg-white rounded-lg shadow-md overflow-hidden">
                    <div class="p-6">
                        <h3 class="text-xl font-bold mb-4 flex items-center">
                            <i class="fas fa-users-cog text-indigo-500 mr-3"></i>
                            并发处理
                        </h3>
                        
                        <div class="space-y-4">
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-17 mr-2">Java 1.7</span>
                                    <span class="font-medium">分段锁</span>
                                </div>
                                <p class="text-gray-600 text-sm">ConcurrentHashMap使用分段锁机制提高并发性。</p>
                            </div>
                            
                            <div class="compare-item p-4 rounded-lg">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-18 mr-2">Java 1.8</span>
                                    <span class="font-medium">CAS+分桶</span>
                                </div>
                                <p class="text-gray-600 text-sm">摒弃分段锁，改用更细粒度的锁和CAS操作，显著提升并发性能。</p>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </section>

        <!-- Visualization Section -->
        <section class="mb-16">
            <h2 class="text-3xl font-bold mb-8 text-center">HashMap 数据结构演进</h2>
            
            <div class="mermaid-container">
                <div class="mermaid">
                    graph LR
                    subgraph Java 1.7
                    A[HashMap] --> B[数组+链表]
                    B --> C[链表长度过长时性能下降]
                    end
                    
                    subgraph Java 1.8
                    D[HashMap] --> E[数组+链表/红黑树]
                    E --> F[链表长度>8转红黑树]
                    E --> G[优化哈希计算]
                    E --> H[改进扩容机制]
                    end
                    
                    A -.->|演进| D
                </div>
            </div>
        </section>

        <!-- Detailed Comparison -->
        <section class="mb-16">
            <h2 class="text-3xl font-bold mb-8 text-center">深入比较</h2>
            
            <div class="bg-white rounded-lg shadow-md overflow-hidden">
                <div class="p-8">
                    <!-- 内存结构和存储 -->
                    <div class="mb-10">
                        <h3 class="text-xl font-bold mb-4 flex items-center border-b pb-2">
                            <i class="fas fa-memory text-indigo-500 mr-3"></i>
                            内存结构和存储
                        </h3>
                        
                        <div class="grid md:grid-cols-2 gap-6">
                            <div class="highlight-box p-4">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-17 mr-2">Java 1.7</span>
                                    <span class="font-medium">链表存储</span>
                                </div>
                                <p class="text-gray-600">所有元素在冲突时都存储在链表中，链表节点的插入和删除操作是O(1)，但查找操作可能会退化到O(n)当链表较长时。</p>
                            </div>
                            
                            <div class="highlight-box p-4">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-18 mr-2">Java 1.8</span>
                                    <span class="font-medium">链表与红黑树结合</span>
                                </div>
                                <p class="text-gray-600">使用链表和红黑树优化存储，短链表保持O(1)操作，长链表转为红黑树提供O(log n)查找性能，显著提升查询效率。</p>
                            </div>
                        </div>
                    </div>
                    
                    <!-- 迭代器和快速失败 -->
                    <div class="mb-10">
                        <h3 class="text-xl font-bold mb-4 flex items-center border-b pb-2">
                            <i class="fas fa-sync-alt text-indigo-500 mr-3"></i>
                            迭代器和快速失败机制
                        </h3>
                        
                        <div class="grid md:grid-cols-2 gap-6">
                            <div class="highlight-box p-4">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-17 mr-2">Java 1.7</span>
                                    <span class="font-medium">传统快速失败</span>
                                </div>
                                <p class="text-gray-600">提供快速失败的迭代器(fail-fast iterator)，在迭代期间如果HashMap结构被修改(除通过迭代器本身的remove方法)，会抛出ConcurrentModificationException。</p>
                            </div>
                            
                            <div class="highlight-box p-4">
                                <div class="flex items-center mb-2">
                                    <span class="version-badge version-badge-18 mr-2">Java 1.8</span>
                                    <span class="font-medium">增强的快速失败</span>
                                </div>
                                <p class="text-gray-600">继续使用快速失败机制，同时改进了迭代器的性能，特别是在处理红黑树结构时的效率。</p>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </section>

        <!-- Key Takeaways -->
        <section class="mb-16">
            <div class="bg-indigo-50 rounded-xl p-8">
                <h2 class="text-2xl font-bold mb-6 text-indigo-800">关键要点总结</h2>
                
                <div class="grid md:grid-cols-3 gap-6">
                    <div class="bg-white p-6 rounded-lg shadow-sm">
                        <div class="text-indigo-500 mb-3">
                            <i class="fas fa-tree text-2xl"></i>
                        </div>
                        <h3 class="font-bold mb-2">红黑树优化</h3>
                        <p class="text-gray-600">Java 1.8引入红黑树处理长链表，将最坏情况下的时间复杂度从O(n)优化到O(log n)。</p>
                    </div>
                    
                    <div class="bg-white p-6 rounded-lg shadow-sm">
                        <div class="text-indigo-500 mb-3">
                            <i class="fas fa-expand-arrows-alt text-2xl"></i>
                        </div>
                        <h3 class="font-bold mb-2">扩容优化</h3>
                        <p class="text-gray-600">改进的扩容机制减少了重新哈希时的性能开销，提升了大数据量下的处理能力。</p>
                    </div>
                    
                    <div class="bg-white p-6 rounded-lg shadow-sm">
                        <div class="text-indigo-500 mb-3">
                            <i class="fas fa-users text-2xl"></i>
                        </div>
                        <h3 class="font-bold mb-2">并发提升</h3>
                        <p class="text-gray-600">ConcurrentHashMap从分段锁改为CAS+分桶机制，显著提升了高并发场景下的性能。</p>
                    </div>
                </div>
            </div>
        </section>
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